remove scheduled release job (#11386)

Author: hubertdeng123

.github/workflows/prepare-release.yml

@@ -8,9 +8,6 @@ on:
       force:
         description: Force a release even when there are release-blockers (optional)
         required: false
-  schedule:
-    # This is when we release the self-hosted repo
-    - cron: "1 18 15 * *"
 jobs:
   release:
     runs-on: ubuntu-latest